For the past couple of years the Lake Winds Energy Park in Mason County, Michigan has been embroiled in a contentious dispute about its noise levels (image to left is the “Park” under construction). In April 2013, five months after the 56 turbines began operating, 17 neighbors filed suit, claiming that wind farm noise, vibrations and flickering lights were adversely affecting their health. A few months later, after commissioning an independent sound study, the Mason County Planning Commission formally declared the wind farm out of compliance and demanded a mitigation plan; the developer, Consumers Energy, disputed the findings yet lost two appeals, one at the Zoning Board of Appeals and one in Circuit Court. During that series of challenges, Consumers developed a plan to modify turbine operations for 7 turbines closest to the four sites where they were found to be marginally too loud.

Marginal is indeed the word: the sound study found 4 locations where the sound level peaked at 0.3 to 1.2 decibels over the 45dBA noise limit (it takes 3dB for a difference between two sounds to be audible); when using 10-minute averages, there were no violations. The various explanations by the consultant, Brian Howe, illustrated the fine line that the turbine operations were walking. His report stressed “general compliance with sound level criteria,” and noted that the brief violations “do not represent a statistically significant portion of time and do not indicate a systemic exceedance.” In his initial testimony at an August Planning Commission meeting, he said that there are no recommendations to correct for these times because “there is not a situation where they are predictably going over 45.” Later, in a November letter to the Commission, after learning that the county had previously decided NOT to allow for occasional exceedances, he stressed that “I can assure the County that competent, material and substantive evidence supports the conclusion that the turbines are not in compliance at certain residences on occasion” and elaborated:

Excursions over 45 dBA should have been anticipated since, as outlined in the acoustic study by Tech Environmental prepared in June 2011, the wind energy park was designed with sound levels identically equal to the 45 dBA criteria at some key receptors with no factor of safety to address the fact that the prediction methodology has a stated accuracy worse than +/- 3 dBA. If Tech Environmental was aware that achieving the criteria even 95% of the time was unacceptable to the County, it would have been prudent to incorporate a suitable safety margin to account for the statistical variation in sound levels.

And this is the first half of the central lesson here: it’s essential that enough of a safety factor is built in to the sound models to account for known variability in sound production (how loud the blades are in various unsteady wind conditions) and sound propagation (how far sound travels as it gradually loses power). Regular readers will know that variability is indeed, as Howe mentioned, often more than the simplified 3dB margin of error that was neglected here (see AEI’s 2012 report). The second half the lesson is related: when noise limits—for the sound of the turbines when it reaches nearby homes—are set as high as 45dBA, they will be regularly audible at these homes, and likely well above night-time ambient sound levels. As many acousticians have stressed for years, these situations are very apt to trigger a significant number of complaints, especially if there are dozens of homes in that nearby range. Here, we had the worst of both worlds: turbine siting plans that pushed sound right at the limit into nearby homes, and a limit that was on the high end of tolerability for many neighbors. Indeed, after one such cautionary report was presented to the Mason County Planning Board, it decided to lower the limit to 40dB, but that change was revoked after push-back from Consumers Energy.

the financial and possible operational details are confidential (2 later additional litigants are yet to settle, but negotiations are ongoing). While many such lawsuits languish, as it can be very hard to prove causality of health effects or a threshold of nuisance, it is always notable when a company decides it’s more advantageous to settle than to push through a court hearing (which was set to begin, with the jury already seated). This is the latest of several such suits that were settled behind closed doors—other high profile compensation cases include Mars Hill, Maine and the Davis family in the UK, while property buy-outs of people who’ve either moved from their homes or become vocal about their issues are widespread, though not common, including a recent buy-out settlement with a family in Vermont, and purchases of multiple homes in Ontario’s Bruce and Dufferin Counties. It’s unfortunate that confidentiality clauses leave the rest of us in the dark, for one of the ways forward is for the wind industry to more willingly compensate those most impacted by their operations, and these cases could offer some guidance as to what level of compensation may be mutually agreeable.

Meanwhile, to the best of my knowledge, Consumers Energy’s challenge to the Mason County demand for mitigation is ongoing; the latest report I’ve found is that the company filed an appeal in July after its loss in Circuit Court. The implications of how that plays out could be far-reaching. The company’s insistence that Howe’s assessment is faulty is based on two related technical points: whether instantaneous exceedances should be considered violations, and whether unattended sound monitoring can reliably identify violations. The latter question gets down into the technical weeds, including accounting for the presence of other ambient noise as well as turbine sounds, and the choice of measurement metric (L90 or Leq, as well as strict adherence to other sound measurement standards identified in the ordinance, which, like many local ordinances, is not necessarily savvy about all the implications and options for measurement). As reported by Michigan Capital Confidential, a good source for coverage of this issue:

Arguing that the County’s decision was an “erroneous ruling,” the utility filed a 38-page appeal with the Michigan Court of Appeals on July 18. In addition, Consumers Energy is saying that if the ruling by 51st Circuit Court Judge Richard Cooper were allowed to stand, it could have an impact on many other wind turbine plants across the state.

“This has implications beyond just Mason County,” Dennis Marvin, spokesman for Consumers Energy told Capitol Confidential. “We believe the study the county based its decision on was flawed. We took this decision (to appeal) very seriously, but ultimately our legal staff determined this was in the best interest of our customers and the landowners at the wind park.”

Rick James, of East Lansing-based E-Coustic Solutions, is an acoustician specializing in the production, control, transmission, reception and effects of sound. According to James, Consumers Energy is not exaggerating when it talks about the potential impact of the Lake Winds case.

“Consumers’ appeal has less to do with the supposed 1 decibel error, the topic of the appeal, and more to do with the wind industry’s broader concerns,” James said. “A decision by the Appeals Court in favor of Mason County would make it easier for other counties and townships with wind energy utility noise regulations to prove non-compliance.”

“Consumers would have been better advised if they had not accepted the conclusions of their acoustical consultant that the proposed project could be fit into the host community without causing problems,” James continued.

In Falmouth, MA we had a similar experience. MassDEP found noise from a wind turbine exceeded state noise regulations and a compromise was reached to shut the turbines down fro 7:00 PM to 7:00 AM. Later the decision was modified to shut the turbines down from midnight to 4:00 AM on the grounds that MassDEP only tested for noise in that time frame. It went before a judge who ruled that the 7:00 PM to 7:00 AM shutdown was a justifiable mitigation plan that avoided the noise nuisance in the neighborhood.

A similar case followed in Fairhaven, MA where the DEP found samples of noise pollution in several neighborhoods. The developer, having learned from the Falmouth case, proposed a mitigation plan that would shut the nearest turbine down from midnight to 4:00 AM when the wind was from the North and less than 8 meters/second in the Winter when it is not raining or snowing. Town authorities accepted the plan persuaded by the argument that since the DEP only took samples under those limited conditions, there is no proof of violations under different circumstances.

A similar case happened in Kingston, MA. If the courts are going to accept such a narrow view of noise pollution violations, then suing and accepting mitigation plans is a meaningless exercise, and a waste of time. In Falmouth there are three identical wind turbines. The mitigation plan only applies to two. In Fairhaven the noise pollution is not significantly reduced. For one thing the sound level is higher above 8 m/s. In Kingston the complaints continue.

Of course the courts are not going to require projects to do better than meet the standard in place; that’s one reason seeing a settlement in Lake Winds is interesting, as many such cases languish. And yes, most violations (at least as measured in short sampling periods) are small and relatively rare, so indeed the mitigations are likely to be minor at best, and not solve the problem for those most affected. These cases, and many others such as the ones you mention, are examples of the risks/costs of having standards high enough to bring clearly audible sound into many homes on a regular basis; once a standard is in place, people will be living with that noise level and some subset of the nearby population will be more impacted by that than others. Falmouth is better off than most in that you got a full night-time shut down; in most cases, such as the proposed plan in Lake Winds, the mitigation is modest operational changes (turbine speed or angle) that slice a decibel or two off the noise level, which is an imperceptible change. (And often, as in Lake Winds, mitigation plans are applied only to turbines that happened to be closest to the testing sites, with many other similar locations in the vicinity not getting even that modest relief; NOTUS in Falmouth is a similar issue). Yet few infrastructure or industrial projects come without some local impact, and in some places these noise levels from turbines trigger less reaction; the subtleties and ambiguities of these issues is something that we’ve covered extensively here, especially in the 2012 and 2011 reports. While Chris’ examples and his final comment on the meaningless of much mitigation provided a nice chance to expand the discussion a bit, the litany of projects with negative impacts on particular communities and families is well-known; I’d rather not rehash them all here. Comments on this case and its implications are more the goal here, rather than reminders of other places where there are noise issues, or general complaints about wind project problems.

Interesting article, Jim. Much of the push-pull between the energy companies and municipalities and residents appears to be arbitrary. Is there any move to some sensible standards so the fight doesn’t have to be fought with each new development? It seems that we should have enough data now to create some good models of forecasted impacts. Also, from what I understand, most of the complaints relate to low-frequency sounds. Is there any good sound-proofing that can reduce the infiltration of these frequencies into a home?

Well, Chris, the big challenge is that there’s no black-and-white threshold that is generally tolerable, except for inaudibility or close to it. Some towns have indeed established setbacks and/or noise limits that aim for this, and some projects are sited (purposefully or fortuitously) at great enough distances to achieve it. To get there, though, we’re talking about setbacks of at least a mile, and the project I visited that was most successful this way is more like a mile and half or two miles from most homes; of course, such setbacks greatly limit potential wind farm sites (or, to take the positive view, focus our wind farm development in areas where problems are least likely to occur). A reasonable approach might be larger setbacks, with readily-obtainable easements to build closer to willing neighbors; most studies and surveys suggest that at least half, and often more, of those living near wind farms are not bothered by the noise, so there should be plenty of sites where projects could proceed with this sort of affirmative buy-in from neighbors, though it would likely involve more compensation payments than are now made, which would also affect budgets and viability of projects.

Meanwhile, though, the primary problem of settling on a generalized “sensible standard” is two-fold. First, the wind industry has plenty of projects they can point to where 45dB sound at homes (or more) didn’t seem to cause problems (though many to most project built in areas densely enough populated to put dozens or hundreds of homes that close have had issues). Second, and related, when audible noise does trigger complaints, it’s usually among a minority of neighbors (often just 5-10%, which is often considered “acceptable” or normal; though in some places, a significant minority of 25-40% are impacted, which is more than I think most project planners or local regulators would expect or like); these proportions are likely due in large part to the spectrum of general noise sensitivity in the population as a whole (20% are very sound-sensitive; another 30% are moderately sound-sensitive and will struggle when the noise is more prominent). Low frequency sound is a big issue, and I tend to think it’s more about the audible low frequencies than inaudible infrasound; these just-audible lower frequencies both travel farther and are less amenable to soundproofing than the higher frequency components of the broad-band turbine sound, so a low pulsing sound (and at times feeling) permeates some homes in some conditions, where, again, the subset of the population that is more sensitive (in perception of sound or reaction/attention to sound) is most likely to be affected. There is some interesting research on infrasound, related to higher peaks than captured in standard recordings using longer sampling times (with the idea being that we may in fact perceive these peaks more readily than audiograms based on long pure tones would suggest), and some possible indications of physiological responses to infrasound below the perceptibility threshold; so far, these lines of research are still in relatively early stages and are in need of replication and ground-truthing in more locations. My feeling is that we know enough about reactions to audible sound to create a workable and livable approach to wind farm siting, and if we do so, it will minimize the possible infrasound issues as well.

My 2011 and 2012 reports go into great detail on these and many of the related challenging issues around wind farm siting and noise. I surely wish there was more openness in the industry to not pushing so close to unwilling neighbors, especially when there are many homes in the area (using the larger setbacks/easements solution mentioned above) and budgeting for noise mitigation payments of various kinds for neighbors within the clearly-audible range (a few property buyouts for those most impacted and more widespread “good neighbor” annual payments that acknowledge the more modest impacts on others)–starting with such policies in place would greatly reduce the fear that grows in many communities that the worst-case things they’ve heard of elsewhere could affect them. Of course, this is rarely done with other kinds of development (roads, factories, etc.), so there’s neither a model nor an incentive for the industry to do so. (However: power plants near homes DO budget for extensive noise control engineering, which can amount to 2-5% of the construction budget, suggesting that budgeting something for proactive solutions is not out of line.)

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